Neumann, Carl. “Theoria nova phaenomenis electricis applicanda.” Annali di Matematica Pura ed Applicata 2, no. 1 (August 1868): 120–128. doi:10.1007/BF02419606. p. 121:
Nova introducitur suppositio, statuendo, causam illam motricem, quam potentiale vocamus, ab altera massa ad alteram non subito sed progrediente tempore transmitti, atque — ad instar lucis — per spatium propagari celeritate quadam permagna et constante. Quam celeritatem denotabimus litera $c$.
Ista suppositio, conjuncta cum hac altera, principium Hamiltonianum normam exprimere supremam ac sacrosanctam nullis exceptionibus obviam, fit suppositio in theoria nostra fundamentalis, ex qua absque ulla ulteriore suppositione leges illæ notissimæ a celⁱˢ Ampère, Neumann, Weber, conditæ sua sponte emanabunt.
My translation attempt:
A new supposition is introduced in making this motive cause, which we call potential, not be immediately but gradually transmitted in time from one mass to another, and—like light—to propagate with a great and constant speed. We will denote this speed by the letter $c$.
This supposition, together with the other, the supreme and sacrosanct principle principle of Hamilton meeting no exceptions, is made fundamental to our theory, from which (without any further supposition) those well-founded laws of the celebrated Ampère, Neumann, and Weber, on their own foundations, will spontaneously emanate.
I'm particularly miffed regarding the last sentence (esp. the abbrevation "celⁱˢ" = "celebrandis" = celebrated/famous?). Did I translate it right?
thanks